1. Field of the Invention
The present invention relates to an improvement of an internal combustion engine in which bearing sections rotatably carrying a camshaft are provided on a cylinder head, and rocker arms moved with the rotation of the camshaft and swingably carried on rocker shafts.
2. Description of the Related Art
Such internal combustion engines are conventionally known, for example, from Japanese Patent Application Laid-open Nos.6-17613 and 10-148113.
In the prior arts disclosed in the above Patent Applications, the rocker shafts are fixed to the bearing sections by bolts passed through the rocker shafts on one diametrical line and fastened to the bearing sections. Therefore, when the fastening of the bolts is only conducted, there is a possibility that the support rigidity of the rocker shafts is sufficient.
There is also an internal combustion engine already known, for example, from Japanese Patent No.2688732 and the like, in which rocker shafts are supported on a rocker shaft holder which includes a plurality of shaft-supporting sections fastened respectively to a plurality of bearing sections of a cylinder head for rotatably carrying a camshaft, and a connecting section connecting the shaft-supporting sections to one another. In this internal combustion engine, it is doubtful that the support rigidity of the rocker shafts is sufficient, because the rocker shafts are supported only by rocker shaft holder.
Accordingly, it is an object of the present invention to provide an internal combustion engine, wherein the support rigidity of the rocker shafts is enhanced sufficiently.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an internal combustion engine including bearing sections rotatably carrying a camshaft and provided integrally or separately on a cylinder head, and rocker arms moved with the rotation of the camshaft and swingably carried on rocker shafts, wherein a rocker shaft holder fastened and fixed to the bearing sections to support the rocker shafts is provided with accommodating recesses into each of which a portion of each of the bearing sections protrudes.
With such arrangement of the first feature, the rocker shaft holder is fastened and fixed to the bearing sections provided on the cylinder head to rotatably carry the camshaft, and the rocker shafts are supported on the rocker shaft holder, and hence, support rigidity of the rocker shafts can be enhanced. Moreover, the accommodating recesses are provided in the rocker shaft holder, and a portion of each of the bearing section protrudes into each of the recesses. Therefore, the fastening structure for the bearing sections and the rocker shaft holder can be formed compactly in a direction of axes of the cylinders, thereby avoiding an increase in size of the engine.
According to a second aspect and feature of the present invention, in addition to the first feature, a portion of each of the bearing sections protrudes into each of the accommodating recesses to avoid the contact with the rocker shaft holder. With such arrangement, it is possible to inhibit the vibration of the camshaft to utmost from being transmitted to the rocker shafts through the rocker shaft holder.
According to a third aspect and feature of the present invention, in addition to the second feature, the plurality of rocker shafts parallel to one another are supported on the rocker shaft holder, and the accommodating recesses are provided in the rocker shaft holder between the rocker shafts. With such arrangement, the fastening structure for the bearing sections and the rocker shaft holder can be formed further compactly in a direction of axes of the cylinders in such a manner that the distance between each of the rocker shafts and the camshaft can be shortened.
According to a fourth aspect and feature of the present invention, in addition to the third feature, the rocker shaft holder includes a plurality of shaft-supporting sections fastened to the plurality of bearing sections and provided with the accommodating recesses, respectively, and a connecting section which integrally connects at least portions of the shaft-supporting sections corresponding to the accommodating recesses to one another. According to a fifth aspect and feature of the present invention, in addition to the second feature, the rocker shaft holder includes a plurality of shaft-supporting sections fastened to the plurality of bearing sections and provided with the accommodating recesses, respectively, and a connecting section which integrally connects at least portions of the shaft-supporting sections corresponding to the accommodating recesses to one another.
With the arrangement of the fourth and fifth features, it is possible to avoid a reduction in rigidity of the rocker shaft holder, in spite of the provision of the accommodating recesses in the shaft-supporting sections.
According to a sixth aspect and feature of the present invention, in addition to the first feature, the plurality of rocker shafts parallel to the one another are supported on the rocker shaft holder, and the accommodating recesses are provided in the rocker shaft holder between the rocker shafts. With such arrangement, the fastening structure for the bearing sections and the rocker shaft holder can be formed further compactly in a direction of axes of the cylinders in such a manner that the distance between each of the rocker shafts and the camshaft can be shortened.
According to a seventh aspect and feature of the present invention, in addition to the sixth feature, the rocker shaft holder includes a plurality of shaft-supporting sections fastened to the plurality of bearing sections and provided with the accommodating recesses, respectively, and a connecting section which integrally connects at least portions of the shaft-supporting sections corresponding to the accommodating recesses to one another. According to an eighth aspect and feature of the present invention, in addition to the first feature, the rocker shaft holder includes a plurality of shaft-supporting sections fastened to the plurality of bearing sections and provided with the accommodating recesses, respectively, and a connecting section which integrally connects at least portions of the shaft-supporting sections corresponding to the accommodating recesses to one another.
With the arrangement of the seventh and eighth features, it is possible to avoid a reduction in rigidity of the rocker shaft holder, in spite of the provision of the accommodating recesses in the shaft-supporting sections.
To achieve the above object, according to a ninth aspect and feature of the present invention, there is provided an internal combustion engine including bearing sections rotatably carrying a camshaft and provided integrally or separately on a cylinder head; and a rocker shaft holder which includes a plurality of shaft-supporting sections fastened to the plurality of bearing sections, respectively, and a connecting section integrally connecting the shaft-supporting sections to one another and which supports a rocker shaft swingably carrying thereon rocker arms and moved with the rotation of the camshaft, wherein the rocker shaft is supported on the shaft-supporting sections and also on shaft-supporting intermediate portions which are integrally provided on the connecting section and each disposed between the adjacent shaft-supporting sections.
With such arrangement of the ninth feature, the shaft-supporting sections of the rocker shaft holder are fastened to the plurality of bearing sections provided integrally or separately on the cylinder head to rotatably carry the camshaft, respectively, and the rocker shaft is supported on the shaft-supporting sections and also on the shaft-supporting intermediate portions integrally provided on the connecting section of the rocker shaft holder and disposed between the plurality of shaft-supporting sections. Therefore, it is possible to sufficiently enhance the support rigidity of the rocker shaft.
According to a tenth aspect and feature of the present invention, in addition to the ninth feature, the rocker shaft supported on the shaft-supporting intermediate portions and another rocker shaft having an axis parallel to such rocker shaft are supported on the rocker shaft holder, and a roller in rolling contact with a cam provided on the camshaft is supported on each of rocker arms swingably carried on the other rocker shaft at locations corresponding to the shaft-supporting intermediate portions, so that they are opposed to the shaft-supporting intermediate portions, and each of the shaft-supporting intermediate portions is provided with a notch for avoiding the interference with the roller. With such arrangement, the rocker arms each having the roller can be disposed sufficiently in proximity to the rocker shaft in spite of the existence of the shaft-supporting intermediate portions, whereby a valve-operating device including the rocker arms and the rocker shafts can be constructed compactly.
According to an eleventh aspect and feature of the present invention, in addition to the tenth feature, rocker arms disposed adjacent the shaft-supporting intermediate portions are swingably carried on the rocker shaft supported on the shaft-supporting intermediate portions. With such arrangement, the axial movement of the rocker arms can be restricted by each of the shaft-supporting intermediate portions, and a part exclusively for restricting the axial movement of the rocker arms is not required and hence, the number of parts can be reduced.
According to a twelfth aspect and feature of the present invention, in addition to the eleventh feature, the rocker shaft holder is integrally provided with ribs which extend in a direction parallel to the axis of the rocker shaft and connects the shaft-supporting sections and the shaft-supporting intermediate portions to each other. With such arrangement, it is possible to enhance the rigidity of the rocker shaft holder, particularly, the rigidity of the shaft-supporting intermediate portions and in turn, to further enhance the support rigidity of the rocker shafts.
According to a thirteenth aspect and feature of the present invention, in addition to the eleventh feature, the rocker shaft holder has an oil sump defined in its upper surface, and lubricating oil passages provided therein for guiding a lubricating oil from the oil sump to slide portions between the shaft-supporting intermediate portions and the rocker arms adjoining the shaft-supporting intermediate portions. With such arrangement, the lubricating oil can be supplied to the slide portions between shaft-supporting intermediate portions and the rocker arms without need of a part other than the rocker shaft holder.
According to a fourteenth aspect and feature of the present invention, in addition to the tenth feature, the rocker shaft holder is integrally provided with ribs which extend in a direction parallel to the axis of the rocker shaft and connects the shaft-supporting sections and the shaft-supporting intermediate portions to each other. With such arrangement, it is possible to enhance the rigidity of the rocker shaft holder, particularly, the rigidity of the shaft-supporting intermediate portions and in turn, to further enhance the support rigidity of the rocker shafts.
According to a fifteenth aspect and feature of the present invention, in addition to the ninth feature, the rocker arms disposed adjacent the shaft-supporting intermediate portions are swingably carried on the rocker shaft supported on the shaft-supporting intermediate portions. With such arrangement, the axial movement of the rocker arms can be restricted by the shaft-supporting intermediate portions, and a part exclusively for restricting the axial movement of the rocker arm is not required and hence, the number of parts can be reduced.
According to a sixteenth aspect and feature of the present invention, in addition to the fifteenth feature, the rocker shaft holder is integrally provided with ribs which extend in a direction parallel to the axis of the rocker shaft and connects the shaft-supporting sections and the shaft-supporting intermediate portions to each other. With such arrangement, it is possible to enhance the rigidity of the rocker shaft holder, particularly, the rigidity of the shaft-supporting intermediate portions and in turn, to further enhance the support rigidity of the rocker shafts.
According to a seventeenth aspect and feature of the present invention, in addition to the fifteenth feature, the rocker shaft holder has an oil sump defined in its upper surface, and lubricating oil passages provided therein for guiding a lubricating oil from the oil sump to slide portions between the shaft-supporting intermediate portions and the rocker arms adjoining the shaft-supporting intermediate portions. With such arrangement, the lubricating oil can be supplied to the slide portions between shaft-supporting intermediate portions and the rocker arms without need of a part other than the rocker shaft holder.
According to an eighteenth aspect and feature of the present invention, in addition to the ninth feature, the rocker shaft holder is integrally provided with ribs which extend in a direction parallel to the axis of the rocker shaft and connects the shaft-supporting sections and the shaft-supporting intermediate portions to each other. With such arrangement, it is possible to enhance the rigidity of the rocker shaft holder, particularly, the rigidity of the shaft-supporting intermediate portions and in turn, to further enhance the support rigidity of the rocker shafts.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.